Amino piperazines and methods of preparing the same



Patented Dec. 22, 1953 AMINO PIPERAZINES AND METHODS OF PREPARING THE SAME Edward A. Conroy, Plainfield, and Robert P. Parker, Somerville, N. J assignors to American Cyanamid Company, New York, N. Y., a corporation of Maine No Drawing. Application June 22, 1951,

, Serial No. 233,126

9 Claims- (Cl; 260256.4)

This invention relates to 1,4-substituted piperazines. More particularly, it relates to l-substituted 4 (N-substituted-amino)-piperazine compounds and methods of preparing the same.

The compounds of the present invention may be illustrated by the following general formula:

in which R is a radical selected from the group consisting of alkyl, aralkyl, monocyclic aryl, carbalkoxy, dialkylcarbamyl and heterocyclic radicals, the bond from the nitrogen in the piperazine ring to the heterocyclic ring being to a group; Y1 and. Y: are selected from the group consisting of hydrogen and methyl; Z is selected from the group consisting of a carbalkoxy, a carbamyl, a thiocarbamyl, and an acyl radical.

The compounds of the present invention being l-substituted 4 (N-substituted-amino) -piperazines, the piperazine ring is shown as saturated. However, in addition to the 1,4-substituents the carbon atoms of the piperazine ring may be substituted as shown at Y1 and Y2. Either Y1 or Y2, or both, may be hydrogen or methyl. The invention therefore contemplates 1,4-disubstituted monoand dimethyl piperazines.

The compounds of the present invention are in eneral crystalline solids. They are only slightly soluble in water or petroleum ether but somewhat more soluble in lower aliphatic alcohols, chloroform, and the like.

The preparation of the new compounds of the present invention may be accomplished in several ways depending, for the most parts, on the nature of the substituent illustrated by Z in the general formula. When Z is a carbalkoxy, a carbamyl or an acyl radical the reaction may be illustrated by the following equation:

in which R is as defined above, X is halogen and R2 is an alkyl, aryl, aralkyl, alkoxy, aralkoxy or radical, the radicals R3 and R4 bein alkyl radicals such as methyl, ethyl, propyl, butyl, amyl, etc., aryl radicals such asphenyl, halophenyl and the like. In introducing an acyl radical into the 1-substituted-4-aminopiperazine molecule an acid anhydride may be used as well'as an acid halide. I

When it is desirable to prepare compounds wherein Z is a mono-substituted carbamyl or thiocarbamyl radical we prefer to prepare the compounds by the addition of an organic isocyanate or isothiocyanate to the appropriate 1- substituted-4-aminopiperazine in a solvent such as diethyl ether. This process may be represented as follows wherein R5 is an alkyl or monocyclicaryl radical:

To prepare those compounds wherein Z is a benzene sulfonyl radical we prefer to react the appropriate 1 substituted 4 aminopiperazine with a benzene sulfonyl chloride in aqueous media in the presence of an acid accepting agent such as sodium hydroxide. This process in which Hal is halogen may be represented as follows:

where the product is in the form, of an oil it 1 can be extracted from the reaction mixture in 1 to the base compounds and similar manner.

The compounds of the present; invention .-are active pharmaceutical prgdiic fless'e'ssihgnactivity as central nervouss system depuessants: anticonvulsants, sedatives, anesthetics and analgesics.

The preparation of compounds*typ icahlofpthe present invention is more fully shown in'tiiefol lowing examples which are given by'wayiofillustration only and notgby way of limitation. All parts are by weight unless otherwise indicated.

Ethyl N (-carbethbmy-Z-pipemzyl)carbamate A1 a lu ns me-i1-car s q eqerbethq ya iaminopip'eraziner ih BQ, parts.- .of absolute :ethanmol sisi suspended; 21 .Q -.-par ts. -.of sodium bicar- .:.-:bonate. The :temperaturef;b usp s is ..-1 kept:ibelowrfiQteC with stirriuge while. a solui:.-ti0nz o ;21 ..5 parts ethylohlorocarbonate in 80 parts of absolute ethanol is added portionwise ai-oven-a periodsoi fifteemrninutes; ,Then; the re- -aaction:-.mixture:5issreflpared; forstwo .hours and .-:.'..=filtered..-. 'Ifhe solventis removed from the filtrate ;;by.- distillation and; the, residual product,- tethyl 35 Z N: (4-1carbethoxy e 1;,piperazylioarbamate; when i3. mether, mmelts at j;'-.-l,4 3;5 -.15l4.5f .0. p i v 1-carbethomy-4-acetyldminopipe'raz'ihe A solution -of"-34.6 parts' of 1' c arbethoxy-4- aminopiperazineand 20.5 parts of acetic anhydrideinil f olparts or I glacial acetic acid is heated on a'wa'ter batlijo'r half an hour. The reaction mixture is then poured into a solution of 500 parts of cold Water-'and ISO partsof concentrated aqueous ammonia (26.5 B.) and the'resulting solntionis extracted with chloroform. The solventisremoyed' fromthe extract by distillation and the residualproduct, l -carbethoxyal -acetyl- :smme i e'raaee; whenfcrystallized fromsacetone, ..Iiielt'siatl1805 i1812021Q te timese le e am rv rms sense essmet-6 ts f.,-ie b i bs aminopiperazine in l'l5sparts of benzene is suspended 26,5';parts of sodaash. The temperature of the suspension is kept'below 50Cs, with stirr ring/While 100 parts of a? 2.0. molar solution of alpha-toluyl'chlofide'imbenzene is added portionwiseovera periodof ten'hifinutes. Then the reactfrommixture is'reflwied for one hourjidiluted tn s atabase e teemparts of 1 carb'ethoxy-i-aminopiperazine and to 4 this is added, over a period of ten minutes, a solution of 18.0 parts of phenyl isocyanate in '75 parts of diethyl ether. During the addition, the reaction mixture is stirred and cooled in an ice- 5.v bath .whileht he product separates from the solution-iaasza white solidi. The product is removed by filtration and crystallized from a mixture of ..acetone and n-hexane. The product, l-phenyl- 3 (a carloethoxy l-p-iperazyDurea, melts at EXAIWPLE 5 i cyel o hezpyl rl e(s -carbethomy-l -pipcrazyl) urea riscflpartssor diethyl ether is dissolved 26.0

parts-of l -icarbethoxy--aminopiperazine and to this is,.added, ,o ver a period of five minutes, a solu- .tioir"of19.0 parts of cyclohexyl isocyanate in 75 parts of diethyl ether. During the addition, the reaction mixture is stirred and cooled in an icebath while the product precipitates from the soluwatiDIlFaS awhitesolida The-productisremoved by infiltration-Rand crystallized .from. a; mixture. of :--acet0ne. and;-n -.he;xane. 'Theproduct; kcyclowhexyl-3 d-carhethoxy-l-piperazyl) urea, .Qlmelts EXAMPLE 6 1 -phenyZ-3- (-carbethoxy-Z -piperazyl) 2 -thz' ourea In 200 parts of diethyl ether is dissolved 34.6

parts of 1-carbethoxy-4-aminopiperazine and 27.0.parts of phenyl isothiooyana te....The product, which slowly separates from the solution upon -standingas av whitej solid',is removedhyfifiltra- .tion and crystallized fromabsolute ethanol." "The product, 1-phenyI-3 (i-carbethoxy-l-piperazyl) 2-thiourea, Inelts'at '189.'0l90.0C.

EXAMPLE 7 40 1-allyZ-3- (st-carbthoxy-Z -piperazyl) Zthiourea Ir'r '20!) parts of diethyl ether is dissolved; "26.0 r parts of l-carbethoxy-t-aminopiperazine 4 and r 15.0 partsofi a'llyl -istntl'iiocyahate. The product, i whiclryslowly;separates fro'm the 'solutionjj-upon -"cooling .as a white; solid, is removed-by filtration and crlystallized'froni a mixture of acetone "and in -"hexane. The, "product,- l-eallyl-3-T i carbethi oxy-l piperaiyl) -2=thiourea,- melts *at 132.0"-

ream c. 7

u EXAMBLE, 8 Ethyl; N? (4e dzethy-Zcarbamybhpipemzyl) sz'carbamate In a;solution'o f.40.0 parts of l'.-.=diethylca'rbamy1- EXAMPLE 9 -l-diethylcarbamyl ai-acetylaminopiperazine A- solution ot 3;? .Q parts ;of --l-diet hylcarbamyleamlnopiperazine. sand -2Q .5.- parts g of; acetic Ianhydride in parts of glacial acetic acid is heat- EXAMPLE 10 1-diethyZcarbamyl-4-benzoylaminopiperazine In 150 parts of a 5% aqueous sodium hydroxide solution is dissolved 37.0 parts of l-diethylcarbamyl---aminopiperazine and to this is added portionwise, over a period of ten minutes, 28.1 parts of benzoyl chloride. During the addition, the reaction mixture is stirred and cooled in an ice-bath while the product separates from the reaction mixture as a viscous yellow oil. The product is removed with the aid of chloroform and the solvent is removed from the extract by distillation. The residue, l-diethylcarbamyllbenzoylaminopiperazine, when crystallized from a mixture of acetone and diethyl ether, melts at, 111.0-112.0 C.

EXAMPLE 11 1 -phenyZ-3- (4-diethylcarbamyZ-1-piperazyl) urea In 150 parts of diethyl ether is dissolved 27.7, parts of 1-diethylcarbamyl-4-aminopiperazine and to this is added, over a period of ten minutes, a solution of 18.0 parts of phenyl isocyanate in 75 parts of diethyl ether. During the addition, the reaction mixture is stirred and cooled in an icebath while the product separates from the solution as a while solid. The product is removed by filtration and crystallized from a mixture of acetone and n-hexane. The product, l-phenyl- 3-(4-diethylcarbamyl-1-piperazyl) urea, melts at 111.0-113.0 C.

EXAMPLE 12 1 -cyclohexyZ-3- (4-0ZiethylcarbamyZ-1 piperazyl) urea In 150 parts of diethyl ether is dissolved 27.7 parts of 1-diethylcarbamyl-4-aminopiperazine and to this is added, over a period of ten minutes, a solution of 19.0 parts of cyclohexyl isocyanate in 75 parts of diethyl ether. During the addition, the reaction mixture is stirred and cooled in an ice-bath while the product separates from the solution as a white solid. The product is removed by filtration and crystallized from n-hexane. The product, 1-cyclohexyl-3-(4-diethylcarbamyll-piperazyl) urea, melts at 98.0-99.5 0.

EXAMPLE. 13

1 -ethyZ-3- 4-diethyZcarbamyZ-1 -p2"perazyl) Z-thiourea In 200 parts of diethyl ether is dissolved 30.0

parts of 1-diethylcarbamyl-4-aminopiperazine The product, 1 ethyl-3-(4-diethylcarbamyl-1- piperazyl) -2-thiourea, melts at 146.0-147.0 C.

EXAMPLE 14 N 4-dz'ethyZcarbamyZ-1 -pz'perazyl) -4-chZorobenzenesulfona'mide In 300 parts of a 10% aqueous sodium hyhours and filtered.

droxidesolutionis dissolved 50.0 parts of l-di ethylcarbamyl-4-aminopiperazine and to this is added portionwise, over aperiod of fifteen minutes, 51.5 parts of fine ground 4-ch1orobenzenesulfonyl chloride. During the addition, the reaction mixture is stirred While the temperature spontaneously rises to 50 C. Stirring is continued'for half an hour at 50 C. and then the reaction mixture is filtered. The White precipitate which forms upon acidifying the filtrate with 50 parts of glacial acetic acid is removedby filtration and dissolved in 200 parts of a 5% aqueous sodium hydroxide. After treating with activated charcoal and filtering, the product is precipitated from the solution by first acidifying with 25 parts of concentrated hydrochloric acid. and then making 'ammoniacal 'with 10 parts of concentrated aqueous ammonia (265 B.). The product, N- (4 diethylcarbamyl l-piperazyl) -4-chlorobenzenesulfonamide, when crystallized from aqueous ethanol, melts at 150.5-151.5 C.

7 EXAMPLE 15 Ethyl-N- (4-methyl-1 -piperazyl) carbamate In a solution of 34.5 parts of l-methyl-4-aminopiperazine in 80 parts of absolute ethanol is suspended 37.0 parts of soda ash. The temperature of the suspension is kept below 50 C., with stirring, while a solution of 32.0 parts of ethyl chlorocarbonate in 80 parts of absolute ethanol'is added portionwise over a period of fifteen minutes. Then the reaction mixture is refluxed for two The solvent is removed from the. filtrate by distillation and the residue is distilled at 3.0 mm., the'fraction boiling at 122-124 C. being collected as the product, ethyl N 44.- me-thyl-l -piperazyl) carbamate.

EXAMPLE 16 I I 1 -cycloheqcyZ-3- (4-methyZ-1 -pzperazyl) urea In 150 parts of diethyl ether is dissolved 23.0 parts of 1-methyl-4-aminopiperazine and to this is added, over a period of five minutes, a solution of 25.5 parts of cyclohexyl isocyanate in parts of diethyl ether. During the addition, the reaction mixture is stirred and cooled in an ice bath while the product precipitates from the solution as a white solid. The product is removed by filtration and crystallized from acetone. The product, 1-cyclohexyl-3- (-methyl-l-piperazyl) urea, melts at 159.5-160.0 C. I

EXAMPLE 17 I 1 -ethyZ-3- (4-methyZ-1-piperazyl) -2-thiourea In 200 parts of diethyl ether is dissolved 34.5 parts of 1-methyl-4-aminopiperazine and 26.0 parts of ethyl isothiocyanate. The ether is removed from the solution by heating on a water bath and the residual product is crystallized from acetone. The product, 1-ethyl-3-(4-methyl 1- piperazyl)-Z-thiourea, melts at 156.2-156.7 C.

EXAMPLE 18 Eth yl N (4-benayl-1 piperazyl) carbamate In a solution of 38.0 parts of 1-benzy1-4-aminopiperazine in parts of absolute ethanol is suspended 26.5 parts of soda ash. The temperature of the suspension is kept below 50 0., with stirring, while a solution of 21.5 parts of ethyl chlorocarbonate in 80'parts of absolute ethanol is added portionwise over a period of fifteen minutes. Then the reaction mixtur is refluxed for two hours and filtered; The solvent is removed from the filtrate by distillation and the residual prod- A solution of 47.8 partslof,.I-benzy1: :@mm piperazine and 25.6 parts of acetiajanhiidridein 150 Pa ts I -8 etis acid. is ;heate i..o a water batnior'halfanhoun. Thdreacti n mi r ture is then pouredinto a, solutiomofi 0 Qartsoi coldwatenand 225 parts oiconceni iatadaquequs ammonia. (2.6.5? B.) and theresultihg SPlu iQ lJs extracted .with .-.ohIorofo1:m. v,Tfi'e; solvent. is I re:

moved. from the ,.extraot..b. distillation and t he residual product. 1-benzgk4+acetylaminopiperazine, when..crysta-llized from ...ac eton e. p1elts Lat sot. em w w em weis m in In 100 parts oibenzene, is. ,dissolved 38.2 parts of l-benayli-aminopiperazine and 30 parts of pyridine; The temperature ofthesolutiomiskept belowhl)? (2., with stirringawhilegfluparts of ,a 1.0

molar solutionv oi .-alpha -..toluyl, ohiorideijn henzene. I added.--portionwise. over ;..a period, fiten minutes. Duringthe addition, a gummnorangecolored precipitate'jorms. e After :heating. the; ,reaction-mixturaon.a.water.bath .ion one hour; the benzene supernateis decanted anddis'cardedand the Tpre'cipitate. is dissolved in v206); partsv of 95% aqueous ethanol The, amber-colored. oil which seriaratesupon diluting. .the, alcoholie; solution with 500 i P rts of .gold. .water is. r m ved. and washed several times with .cold. Water whereupon it crystallizes to a lyellow, solid. This product, 1 benzyl-4-phenylapetylan inopiperazine, when crystallized from acetone; melts at 16l.0-161.7 C.

Emma-21: V

1-benzyl-4-benzoylaminopipemzinei.

In-.200..par.ts..o a 5%, aqueous sodiurn, hydroxide solution .dissolyed 473. parts of ,.l-b enzyl-.4" minop e az ns' m rt lth sis addesii or ionw se. v r a p riod-off .t n.mi11.utes,..3.5.2 pa tsfoibsnzoyl chloride. Durin i'hfifiddi'ti'on. the reaction mixture. is stirred and .cooled in. an ice-bath while the product\separates iromthe reaction mixture as, a yellow. solid; The .prod'uc. i removed with c the aid of chloroform and-thesolvent is removed from the extract by distillation. The residue, 1- benzyl-4-benzoylaminopiperazine, when crystallized from acetone .melts at ;.1 l3.Q". 1-74 .ll.-..C,

nxAmLsizz 1 -phenyl-3 -'C4'+benzyl-1 wipemzyl) areas In 100. parts. of. methyl; ether is. dis olved 2815 parts of.l-benzyl -aminopiperazine andtothis is added, over. a period of fifteen minutes: 9. solution of 18.0 parts ofphenylisocyanate in 50' parts of diethyl ether. During the addition, the reaction mixture is stirred .and-.-cooled in an ice-bath while the prpductisenarates. from the solution as a White solid. The product is'removed' by fil-,

tration and erystal-lizedwfrom --aqueous. ethanol. The-produot,-l -phenyI-3'-(4 benzyl l piperazylrurea;{melts at- 135.0 135s5 C.

m 100 parts 1 of' dietlfryl' ether-is di-ssolvedass parts ofl benzyl i-aminopiperazineand to this from chloroform, melts at- 23815'-239'.0 C.-'

t q io ..5..p ;ts oi -p enyl; i thiqoy pato 50.narts.of,dieth .e herurinst ea ditio the..rsact onmixtu js stirred. a d; c ledin. a ice-bath. .w le. t e. p o st s parate .i t e solutionasa whit 's is ...1. eip q uots moys h tratiqn-ands yst izedfrom a m xtu eof acetone aniabsolute ethanol. The product, 1 ph n L-B .-.b nzy1 7- 1 -.p p.eraz 2 ;t io-. urea melts. at. 180;5.?1 182-.0? ZC.

Ethyl N [4 (4 adihmpltazwl) I pivot-asy carbama e.

A solution of 42.3 parts of 1-(4-chlorophenyD- -aminopiperazine 13:116.,{20153 parts of. acetic, anhydlidfiii-II; iEQuparts of glacial.- acetioacidiis heated on; a. waterebath for-.haltan 130121 The. reaction mi-xtureris rpouwedz. into- 500 parts. of .cold watertwhereupon-.tl1e@r roduet; separates fromthe solutiomes a white :solid; and: is removed-by. .filtratiom. The eproduot. 1' ,1-.(.4;-ch1or0pi1enyl 14- a etylamin piperazinm r when :cmlstallized from absolute iethanoli;melts':at.;21l:5?+213:0"

. XA LE 1 ph nyl 3 [4 4 chz m n zr. 1 pipemzyZ-lurea In 1750-,partspf ,d-iethyl ether is'dissolved 42 .3 parts of l-(4-chlorophenyll-4-aminopiperazine and to this is added a solution of 24.0 parts of phenyl' isocyanate in partsof dieth-ylether. The product separates from the solution as a white solid andis removed by filtration; The product,- 1 7 phenyl 3 [4 (4 chlorophenyh piperazyllurea when crystallized from chlorobenzene, melts at -23( l'-.5-231;0 C.

EXAMPLE; 27- i a 1' (2.---chZ0rophenyZ-- 3 {4- (.4 chlorophenylll-piperaayl lurew In 400 parts of diethyl ether is dissolved 21.2 parts of l-(-chlorophenyl)-4-aminopiperazine and tothisisaaddeda solution-of. 15.4 parts of ochlorophenyl' isooyanate inflfi parts of diethyl ether. The product separates from the solution as-a white-solid and is removed byfil-tration. The product; 1 #42 "chlorophenyl)-'-- 3 [4. (4 -chl'orophenyl)-1-pi1oerazyllurea, when I crystallized.

EXAMPLE 28 1,1; diethyli..- 3 [4 (4 ch lorophenyl) 1- piperaeyllu ew In 1,200 parts of diethyl-ether is dissolved 84.6 parts. .of lchloropl enyl). rdraminopiperazine and 27.1 partsof. diethylcarbamyl chloride. The reaction mixture is allowed to stand at 2535 C.

for severaldaysandis then filtered. The solvent is removed from'the filtrate'loy distillation and the residual product, 1,1-diethyl-3-l4-(4 -chlorophenyl) -1-piperazyl]urea, when crystallized from n-hexane, melts at 1'0 8.5'-109.0 C

EXAMPLE-29 1 allyl 3 [4 (4 chlorophenyl) 1 -'p2'percal/l] -2-thiourec In 750 parts of diethyl ether is dissolved 42.3 parts of l-(4-chlorophenyl)-4-aminopiperazine and 20.0 parts of allyl isothiocyanate. The prod* uct, which slowly separates from the solution. upon standing as a white solid, is removed by. filtration and crystallized from absolute ethanol. The product, 1-a11y1-3-[ l -(d-chlorophenyl) -l-' piperazyll-Z-thiourea, melts at 198.5 -200.0 C.

EXAh IPLESO Ethyl N [4- (Z-pyridzfl) Bpiperazyl] carbamate In a solution of 35.0 parts of l-(Z-pyridyD-4- aminopiperazine in 80 parts of absolute ethanol is suspended 26.5 parts of soda ash. The temperature of the suspension is kept below 50 C.,' with stirring, while a solution of 21.5 parts .of ethyl chlorocarbonate in 80 parts of absolute ethanol is added portionwise over aperiodof fifteen minutes. Then the reaction mixture is refluxed for two hours and filtered. The solvent is removed from the filtrate by distillation and the residual product, ethyl N-. [34.- (Z-pyridyl) -1-piperazyll carbamate, when crystallized from diethyl ether, melts at 133.0-l34.0 C.

EXAMPLE 31 1 (Z-pyridyl) -4-acetylaminopipemainc A solution of 35.7 parts of 1-(2-pyridyl) -4aminopiperazine and 20.5 parts of acetic anhydride in 150 parts of glacialacetic acid is heated on a water bath for half an hour. The reaction mixture is then poured into a solution of 500 parts of cold water and 180 parts of concentrated aqueous ammonia (265 B.) and the resulting solution is extracted with chloroform. The solvent is removed from the extract by distillation and the residual product, 1-(2-pyridyl)-4-acetylaminopiperazine, when crystallized from acetone, melts at 1'72.5-l73.5 C.

EXAMPLE 32 1 -phenyZ-3- 4- (Z-pyridyl) -1 -piperazyll urea In 350 parts of diethyl ether is dissolved 35.0 parts of 1-(2-pyridyl)-4-aminopiperazine and to this is added, over a period of ten minutes, a solution of 24.0 parts of phenyl isocyanate in '75 parts of diethyl ether. During the addition, the reaction mixture is stirred and cooled in an icebath while the product separates from the solution as a white solid. The product is removed by filtration and crystallized from acetone. The product, 1-phenyl-3-[4-(2-pyridyl) 1 piperazyllurea, melts at 179.0-180.0 C.

EXAMPLE 33 g 1 -alZyZ-3- [4- (Z-pyridyl) -1 -piperazyll -2-thiourea In 300 parts of diethyl ether is dissolved 35.0 parts of 1-(2-pyridyl)-4-aminopiperazine and 20.0 parts of allyl isothiocyanate. The product, which slowly separates from the solution upon cooling as a white solid, is removed by filtration and crystallized from absolute ethanol. The product, 1-allyl-3-[4-(2-pyridy1) -1-piperazyl] -2- thiourea, melts at 155 .0";- 156 .0 C.

hydroxide solution.

N- [4- (Z-pyrz'dyl) 1-piperazyll -4-chl orobenzen. esulfcnamide In 500 parts of a 10% aqueous sodium hydroxide solutionis dissolved 35.? parts of 1-(2-pyridyl) -4-aminopiperazine and to this is added portionwise, over a'period of fifteenminutes, 42.2 parts of finely ground 4.-chlorobenzenesulfonyl chloride. During the. addition, the reaction mixture is stirred while the "temperature 'spontaneously rises to 50 C. Stirring is continued for half an hour at 50 C. and then the reaction mixture: is filtered. The yellow precipitate which forms upon acidifying the filtrate with parts of glacial acetic acid is-removed by filtration and dissolved in 600 parts of a 5% aqueous sodium After treating with 'activated 'charcoal'and filtering, the product is precipitated from the solution by acidifying with 50 parts of glacial acetic acid. The product, N-[4- (Z-pyridyl) -1 -pi peraz yl1-4-chlorobenzenesulionamide, when crystallized from absolute ethanol,

melts at 17305-1745 C. with decomposition. EXAMPLE 35 Ethyl N- [4- (Z-pyrzm'z'dyl) -1-piperazyl] -carbcmate f In a solution of26.9 parts of 1-(2-pyrim'idyn 4-aminopiperazine'in"15(l parts of absolute ethanol is suspended 21.0 parts of soda ash. The

temperature of the suspension is kept below 50 C., with stirring, while a solution of 16.2 parts of ethyl chlorocarbonate in 80 parts of absolute ethanol is added portionwise over a period of ten minutes. Then the reaction m xture is refluxed for one hour and filtered while hot. The product separates as white crystals from the filtrate upon cooling and is removed by filtration. The product, ethyl N- [4-(2-pyrimidyl) -1-piperazyl] carbamate, when crystallized from a mixture of acetone and n-hexane, melts at 186.5-187.5 C

EXAMPLE 36 1- (Z-pyrz'midyl) -4-acetylaminopiperazine EXAMPLE 37 1 -cyclohe:cyZ-3- [4- (Z-pyrimidyl) -1 -piperazyll urea In parts oi. diethyl ether is dissolved 35.8 parts of 1-(2-pyrimidyl)-4-aminopiperazine and to this is added, over a period of five minutes, a solution of 25.5 parts of cyclohexyl isocyanate in 75 parts of diethyl ether. During the addition, the reaction mixture is stirred and cooled in an ice-bath while the product separates from the solution as a white solid. The product is removed 7 by filtration and crystallized from acetone. The product, 1 cyclohexyl-3- [4- (Z-pyrimidyl) -1-piperazyllurea, melts at 200.5-201.5 C.

I-eth'yZ-Zi-"M-(z-pyrimidyli -1-piperazyl] -2- thiomea In 200 parts of diethyl ether is dissolved 35.8 parts of 1-(2-pyrimidyl) -4'-aminopiperazine and 17.4 parts of ethyl isothiocyanate. The ether is removed from the solution by heating on a water bath and the residual product is crystallized from absolute ethanol. The product, 1-ethy1-3-[4-(2- pyrimidyl)'-1-piperazy1l -2-thiourea, melts at 206.5-208.0 C.

We claim: 1; Compounds having the general formula:

in which R and Z are a. lower earbalkoxy radical. 2. Compounds having the general formula:

in which R is the Z-pyridyl radical and Z is a lower carbalkoxy radical. J

3. Compounds having the general formula:

in which R is a. benzyl radical and Z is a carbamyl radical. v i y 4. Ethyl N-(4-carbethoxy-1-piperazyl) carbamate.

12 r v 5. Ethyl N- [4- 2-py11dyn -1-piperazyll carbamate.

6. 1-pheny1-3-(4-benzyl-1-piperazy1)urea.

7. l-allyl-3- [4- (-ehlorophenyl) -1-piperazyl] 2-thiourea.

8. Ethyl N- [4-. (2-pyrimidyl) -1-piperazy1] carbamate.

9. Compounds of the group having the formula:

in which R is a. radical selected from the group consisting of lower alkyl, monooyclic aralkyl, dicyclic aralkyl, monocyclic aryl. lower carbalkoxy,

'di-lower-alkylcarbamyl, pyridyl and pyrimidyi radicals in which the bond from the nitrogen in the piperazine ring to the heterocyclic ring is to a EDWARD A. CONROY. ROBERT P. PARKER.

No references cited. 

9. COMPOUNDS OF THE GROUP HAVING THE FORMULA: 